The present invention relates to shift (or changeover) control apparatus and method for an automatic transmission adapted to transmit a power by engaging a clutch (or friction-engagement element) according to the shift, and more particularly to shift control apparatus and method in which the engaged clutch is controllably changed from a first clutch (first friction-engagement element) to a second clutch (second friction-engagement element) when the shift is carried out.
Generally when carrying out a shift of automatic transmission (when changing a shift-step), a friction-engagement element such as a clutch is changed from a disengaged state to an engaged state, or changed from the engaged state to the disengaged state. In such a case, it is desired that an operation for the friction-engagement element is performed smoothly and quickly so as not to generate a shock at the time of the shift. Hence, the following techniques are disclosed. A Japanese Patent Application Publication No. 1997(H09)-170654 exemplifies a previously proposed control apparatus. In this technique, a hydraulic pressure to a hydraulic servo of friction-engagement element is adjusted in order to reduce the shock generated at the time of the shift. Moreover, a Japanese Patent Application Publication No. 2000-110929 exemplifies a previously proposed control apparatus. In this technique, when an input torque of the transmission is varied during the shift during which a changeover of friction-engagement element is conducted; a working fluid pressure for engagement-side element (i.e., friction-engagement element to be engaged) or a working fluid pressure for disengagement-side element is varied to its value corresponding to the varied input torque, point by point, by checking the variation of input torque of the transmission.